Anamorphic lens
From The Glossary of Digital Photography
A lens designed to squeeze a very wide image, thus distorting it, to fill a frame of film. This provides a higher-quality image when using an existing film size because the entire film area is used. When the image is shown at a theater, it is shown back through an anamorphic lens to unsqueeze the image and remove the distortion before the projected image hits the screen. The same is done digitally with images and movies stored on DVDs. This technique increases the apparent resolution of the images and movies played back on a widescreen without using the black bars or letterbox format.
